On trees and imagination

I recently heard the question "What scientific fact is the hardest to believe?" I think I could come up with a different answer to that each time it's asked or each time I think of a different area of science. In this case, I was walking, saw a tree, and I thought about the amazing fact that it's one of my relatives.

We share an ancestor with a tree--or a mushroom or any other living thing on earth. My great great great........great grandpa was also the grandpa of that tree. That ancestor lived about 2 billion years ago, so we aren't exactly first cousins, but we share an ancestor nonetheless. Sometimes I have students who think that evolution only means we are related to monkeys, or other mammals, or other vertebrates. They find it very strange we are related to a mosquito, and harder yet that we are related to a tree.

Perhaps the most common argument against evolution is the argument from personal incredulity. A person sees some complex contrivance such as the eye, they can't imagine how it would arise in many small steps, and thus declare that it couldn't have. It never occurs to them that their ability to imagine something is not evidence. It is hard for people to imagine how an eye or a wing could possibly arise. And yet not only are our eyes related to those of other animals, molecules in them can be found in a tree or a bacterium.

Sometimes science is characterized as rigid, logical, or technical. Imagination is for the arts or humanities. But here we find that science tells us something is true that our imaginations cannot even grasp. Science and the world is stranger and bigger than our imaginations. Those who deny evolution are the ones limited to a rigid and unimaginative world.

Science doesn't just say something is true, it gives us the tools and evidence to see it, to imagine the unimaginable. When I teach cell biology, I spend most of the time talking about just a generic cell, not a human cell or a plant cell. A tree and a human might seem very different, but the molecular processes and cellular structures are the same in many ways. It is when you look at the cell that you see our relatives. William Paley argued that our eye is an amazing piece of engineering, more intricate than a watch. Yet the protein and pigments in our eye are also found in a bacterium, another of my relatives.

Science doesn't limit the imagination, it fires it. What could be more cool than going for a walk in the shade of your relatives, and being able to see the family resemblance.